Detergent compositions normally contain surfactants which tend to produce foam when agitated in aqueous solution. For many applications, especially in automatic washing and dishwashing machines, excess foam production is a serious problem and with many effective surfactants, it is necessary to add foam suppressing or controlling agents in order to prevent suds-overflow from the machine or under-usage of product by the user. On the other hand, consumers normally expect and prefer a certain amount of foam to be present and, indeed, research has shown that consumers are highly sensitive to a reduction in the foam level pattern. In any particular application, therefore, the optimum degree of foaming will be sufficiently low to avoid oversudsing under all conceivable washing machine temperatures, load and soil conditions, but sufficiently high to meet the consumers preference for a moderate to generous level of foam.
Detergent compositions currently sold for the European domestic automatic washing machine market generally contain up to about 12% of organic surfactant and for such compositions, suds-suppressors satisfying the above constraints are now well established. For example, in No. EP-A-46342, it is taught to use a polydimethylsiloxane/hydrophobic silica suds-suppressor in the form of a dispersion in an ethoxylated nonionic surfactant using certain siloxane-oxyalkylene copolymers as dispersing agent. In No. EP-A-8829, a suds-suppressor is disclosed consisting of a major portion of wax together with a nonionic dispersing agent and hydrophobic silica. No. GB-A-1,407,977 discloses protection of a polydimethylsiloxane/silica suds-suppressor in a water-soluble dispersible carrier.
In detergent compositions containing a high level of surfactant, however, (in excess of about 12%) problems of foam control in front-loading automatic washing machines become increasingly intractible. Thus, the technique of dispersing polydimethylsiloxane/silica in nonionic surfactant is found to become impractical at high levels of suds-suppressor because of diminishing dispersion stability. The wax/silica/dispersant systems are also found to be deficient because of their inherently slow kinetics; in other words, the rate of release of wax/silica fails to match the rate of transport of surfactant to the air/water interface. Conventional polydimethylsiloxane/silica suds-suppressors are also deficient for foam control in high active detergent compositions, presumably because the polydimethylsiloxane is rapidly dispersed or solubilized by the higher surfactant levels. Furthermore, these problems of foam control are found to be greatly exacerbated in concentrated surfactant systems containing C.sub.10-16 anionic or cationic surfactants which are known to have strong foam-generating characteristics.
The present invention thus provides a suds-suppressor composition suitable for addition to a high active heavy duty detergent composition to provide improved foam control characteristics. It further provides a detergent composition containing a high level of organic surfactant and having improved foaming characteristics across the range of wash temperature conditions. It also provides a high active detergent composition containing C.sub.10-16 anionic and/or cationic surfactants and having improved foaming characteristics under varying wash temperature, product usage, soil, load and rinsing conditions.